Netty：作用场景。
1）Netty可以基于socket实现远程过程调用（RPC）。
2）Netty可以基于WebSocket实现长连接。
3）Netty可以实现Http的服务器，类似于Jetty，Tomcat等Servlet容器。
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Netty充当Http服务器，我们通过浏览器去访问服务器的资源，服务器端处理完之后给我们返回响应—–Helloworld。
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1）定义一个Server
1 package com.foreign.netty.helloworld;
2
3 import io.netty.bootstrap.ServerBootstrap; 4 import io.netty.channel.ChannelFuture; 5 import io.netty.channel.EventLoopGroup; 6 import io.netty.channel.nio.NioEventLoopGroup; 7 import io.netty.channel.socket.nio.NioServerSocketChannel; 8 9 /** 10 * Created with IDEA 11 * author:foreign 12 * Date:2018/12/25 13 * Time:23:21 14 */ 15 public class TestServer { 16 public static void main(String[] args) throws InterruptedException { 17 /** 18 * 两个事件循环组(死循环) boos接受连接并发送给worker 19 */ 20 EventLoopGroup bossLooper = new NioEventLoopGroup(); 21 EventLoopGroup workerLooper = new NioEventLoopGroup(); 22 23 try { 24 /** 25 * ServerBootstrap 服务端启动 26 * NioServerSocketChannel 通道（反射） 27 */ 28 ServerBootstrap serverBootstrap = new ServerBootstrap(); 29 serverBootstrap.group(bossLooper, workerLooper).channel(NioServerSocketChannel.class).childHandler(new TestServerInitializer()); 30 31 ChannelFuture channelFuture = serverBootstrap.bind(8899).sync(); 32 channelFuture.channel().closeFuture().sync(); 33 } finally { 34 bossLooper.shutdownGracefully(); 35 workerLooper.shutdownGracefully(); 36 } 37 } 38 }
2）定义一个Initializer
1 package com.foreign.netty.helloworld;
2
3 import io.netty.channel.ChannelInitializer; 4 import io.netty.channel.ChannelPipeline; 5 import io.netty.channel.socket.SocketChannel; 6 import io.netty.handler.codec.http.HttpServerCodec; 7 8 /** 9 * Created with IDEA 10 * author:foreign 11 * Date:2018/12/25 12 * Time:23:32 13 */ 14 public class TestServerInitializer extends ChannelInitializer<SocketChannel> { 15 16 /** 17 * 子处理器， channel被注册好，会被自动创建 18 * @param ch 19 * @throws Exception 20 */ 21 @Override 22 protected void initChannel(SocketChannel ch) throws Exception { 23 ChannelPipeline pipeline = ch.pipeline(); 24 //编解码 25 pipeline.addLast("httpServerCodec",new HttpServerCodec()); 26 //自己定义的handler 27 pipeline.addLast("testHttpServerHandler",new TestHttpServerHandler()); 28 29 } 30 }
3）定义一个Handler
1 package com.foreign.netty.helloworld; 2 3 import io.netty.buffer.ByteBuf; 4 import io.netty.buffer.Unpooled; 5 import io.netty.channel.ChannelHandlerContext; 6 import io.netty.channel.SimpleChannelInboundHandler; 7 import io.netty.handler.codec.http.*; 8 import io.netty.util.CharsetUtil; 9 10 import java.net.URI; 11 12 /** 13 * Created with IDEA 14 * author:foreign 15 * Date:2018/12/25 16 * Time:23:34 17 */ 18 public class TestHttpServerHandler extends SimpleChannelInboundHandler<HttpObject> { 19 /** 20 * 把结果返回给客户端（回调） 21 */ 22 @Override 23 protected void channelRead0(ChannelHandlerContext ctx, HttpObject msg) throws Exception { 24 if (msg instanceof HttpRequest) { 25 26 HttpRequest httpRequest = (HttpRequest) msg; 27 28 //获取请求的方法类型 29 System.out.println(httpRequest.method().name()); 30 31 URI uri = new URI(httpRequest.uri()); 32 if("/favicon.io".equals(uri)) { 33 System.out.println("请求了favicon.io 图标"); 34 return; 35 } 36 37 ByteBuf content = Unpooled.copiedBuffer("Hello Netty", CharsetUtil.UTF_8); 38 FullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK, content); 39 response.headers().set(HttpHeaderNames.CONTENT_TYPE, "text/plain"); 40 response.headers().set(HttpHeaderNames.CONTENT_LENGTH, content.readableBytes()); 41 42 ctx.writeAndFlush(response); 43 44 ctx.channel().close(); 45 } 46 } 47 }
4）gradle的配置
plugins { id ‘java‘ } group ‘com.foreign‘ version ‘1.0-SNAPSHOT‘ apply plugin: ‘java‘ sourceCompatibility = 1.8 targetCompatibility = 1.8 repositories { mavenCentral() } dependencies { implementation ‘io.netty:netty-all:4.1.10.Final‘ testCompile ( "junit:junit:4.11" ) }
5）运行结果：运行server，并访问该地址。
6）总结：
1）在TestServer类中，启动一个ServerBootStrap的服务器，里面有两个事件循环组，并且通childHandler关联处理器。
2）在TestServerInitializer中加载netty内置的handler和自己的handler。
3）在TestHttpServerHandler中返回数据到客户端。